Microprocessors, memory devices, field-emission-displays, read write heads and other microelectronic devices generally have integrated circuits with microelectronic components. A large number of individual microelectronic devices are generally formed on a semiconductor wafer, a glass substrate, or another type microelectronic workpiece. In a typical fabrication process, one or more thin metal layers are formed on the workpieces at various stages of fabricating the microelectronic devices to provide material for constructing interconnects between various components.
The metal layers are often applied to the workpieces via electrochemical plating in an electroplating reactor or machine. A typical electroplating reactor includes a container for holding an electroplating solution, an anode in the container to contact the electroplating solution, and a support mechanism having a contact assembly with multiple electrical contacts that engage the seed-layer. The electrical contacts are coupled to a power supply to apply a voltage to the workpiece. In operation, the front surface of the workpiece is immersed in the electroplating solution so that the anode and the workpiece establish an electrical field that causes metal ions in the electroplating solution to plate out onto the workpiece.
In so-called “wet-contact” reactors, the electrical contacts are exposed to the electroplating solution during a plating cycle. Consequently, the metal ions in the electroplating solution also plate out onto the contacts. The contacts, however, may plate at different rates with the result that some contacts can have a relatively greater or lesser surface area contacting the workpiece, as plated-on metal builds up on the contacts over time. This reduces the uniformity of the metal layer plated on the workpiece. It can also contaminate the workpiece via poorly adhering metal particles separating from the contacts and depositing onto the workpiece. To avoid this result, the contacts must be periodically “de-plated” to remove the metal that plates onto the contacts during a plating cycle, as part of ongoing maintenance of the reactor.
Typically, the contacts are deplated by immersing the contact assembly into the plating solution while passing reverse electrical current through them. The reverse current causes the plating cycle to reverse, moving metal off of the contacts and back into the solution. However, the reverse current must be limited to avoid degrading the plating solution. The rate of deplating is also limited by amount of agitation that can be provided to the plating solution around the contacts. Consequently, the contact deplating operation takes significant time to complete. This reduces the throughput or use efficiency of the electroplating reactors. Accordingly, improved designs for deplating contacts are needed.